PROJECT SUMMARY/ABSTRACT Mutations that cause chromosome instability (CIN) are considered important predisposing events that contribute to the initiation and/or progression of cancer. Our approach is to develop and apply genetic and biochemical methodologies to obtain an understanding of molecular components required for chromosome transmission, with the overarching goal of relating our work in yeast to human cancer. The specific aims are: 1. To characterize essential CIN genes/pathways: shortened telomere CIN genes and the ASTRA complex. We will dissect the function of the ASTRA complex and its role in telomere biology and TORC1 signaling. 2. To characterize the roles of DNA damage and RNA processing in genome integrity. Five subunits of the mRNA cleavage and polyadenylation factor (CPF) exhibit CIN and high rates of spontaneous Rad52-foci while splicing factors show wild-type levels of damage. We will characterize the mechanism by which the CPF complex and other RNA processing factors cause DNA damage and/or CIN. 3. To validate candidate somatic mutations in CIN genes involved in telomere biology and RNA metabolism, and assess sensitization of cells to knockdown of candidate synthetic lethal partners. We will evaluate methods in yeast to determine whether specific mis-sense somatic mutations found in tumors are functional and test synthetic lethal interactions predicted from yeast genetic interaction networks for evolutionary conservation in cultured mammalian cells. Further elucidation of the genetic basis of CIN in yeast will provide a mechanistic basis for understanding this process in human cells, and will provide candidate genes for those CIN genes mutated in cancer. Therefore, knowledge gained from this work will provide insight into tumorigensis. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page